Growth and characterization of epitaxially aligned titanium nitride thin films on silicon by orthogonally crossed-beam pulsed laser deposition

TiN thin films have been grown epitaxially on Si(111) substrates by crossing orthogonally a pulsed molecular N₂ jet with a pulsed-laser generated Ti plume. This so- called reactive crossed-beam pulsed laser deposition technique was demonstrated as a modification of conventional pulsed laser deposition and was used to grow high quality binary compound materials. Time-of-flight (TOF) measurements of species impinging onto the substrate were performed using an in-situ ion probe, and these measurements were used to optimize the growth conditions. Average plume kinetic energies ranged from 45 to 155 eV. Under essentially fixed N₂ jet conditions, the crystallographic quality of the films was found to be a stronger function of kinetic energy than growth temperature, with optimal films resulting for a plume mean kinetic energy of ~ 92 eV and substrate temperatures near 750 °C.

Scattering processes within the interaction regime were explained by Singh's model and it was determined that the processes between the laser plume and the pulsed gas expansion were responsible for the enhanced reactivity in crossed-beam PLD.

Film-growth mechanisms and microstructure were investigated using in-situ reflection high energy electron diffraction (RHEED), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and scanning transmission electron microscopy (STEM). It was found that TiN thin films grow essentially in a Stranski-Krastanov growth mode under optimal growth conditions. Although TiN is highly mismatched with respect to Si (lattice constant mismatch of 22.3%), single crystal TiN/Si heterostructures are entirely feasible through a process known as domain-matching epitaxy. The epitaxial relationship between TiN and Si by domain-matching epitaxy is discussed in detail in this thesis.

The crystalline quality and electrical properties of the films were investigated using X-ray diffraction and four-point Van der Pauw measurements, respectively. Films grown under optimal conditions were highly textured and had mosaic spreads of ~18 arc- min and ~26 arc-min for a rocking curve around the TiN(111) pole and a ø-scan through the TiN(002) pole, respectively. All the films showed metallic behavior with resistivities that varied linearly with temperature above 75 K. The best film had a room temperature resistivity of 3.76 µ2-cm. Implications of low-resistivity epitaxial TiN/Si heterostructure device fabrication are discussed.

Full-Potential Linearized Augmented Plane Wave (FLAPW) density functional theory (DFT) calculations, as implemented in the WIEN97 codes, have been employed to compare experimental electron energy loss spectroscopy (EELS) results with theoretical calculations since the cross section of electron near-edge structure (ELNES) is proportional to the unoccupied density of states. The implications of these results are discussed.